1. Field of the Invention
The present invention relates to an image forming apparatus in which an image formed surface is subjected to laminate processing, and more particularly, it relates to an image forming apparatus comprising a recording portion for effecting recording on a recording medium by discharging ink from a recording means and a laminating portion for effecting laminate processing on the recording medium after image formation.
2. Related Background Art
Image forming apparatuses having a printer function, a copier function or a facsimile function, or image forming apparatus used as an output equipment of a composite electronic device including a computer or a word processor, an output equipment of a work station or an output equipment of a digital camera, have been designed to form an image (including characters and/or symbols) on a recording medium such as a recording paper or a plastic sheet in response to image information. Such image forming apparatuses can be classified into ink jet type, wire dot type, thermal type and laser beam type in dependence upon their recording systems.
Among them, an image forming apparatus of ink jet type (ink jet recording apparatus) is designed to form the image on the recording medium by discharging ink from recording means (recording head) so that the recording means can be made compact, a highly fine image can be formed at a high speed and the image can be formed on a plain (normal) paper without special processing. Further, there are advantages that a running cost is low, noise is reduced due to a non-impact system and a color image can easily be formed by using plural kinds of inks (for example, color inks).
However, since the ink jet recording apparatus mainly uses liquid ink, in order to obtain a high quality image, one of important subjects is how to dry the ink properly. It is general to use a recording medium having an ink receiving layer in order to obtain the high quality image. However, since the ink receiving layer is apt to absorb the ink, if the recording medium is wetted by water after the image formation, the ink will be solved to distort the image or reduce density or to transfer the image also to a rear surface of the recording medium or curl the recording medium. On the other hand, if dye having good color reproduction is used, although sharp color saturation can also be achieved, due to illumination of light and gas such as ozone, dye attack is generated to cause discoloring.
In order to solve these problems, there has been proposed an apparatus for laminating an imaged surface with a film. Since the imaged surface can be covered by lamination, excellent water proof and gas proof can be achieved, and a light-resistance property can be enhanced by using UV cut material in the laminate layer, thereby improving weather-resistance totally. Further, good appearance and quality can be added to the output image by changing surface properties (for example, mirror surface property, mat property and the like) of the laminate layer and/or color and thickness of the laminate itself.
FIG. 9 shows a conventional laminating apparatus. A recording medium 213 is conveyed in a direction shown by the arrow P. When the recording medium is located at a position 213a, an image has already been formed on an upper surface of the recording medium. Moisture included in the recording medium 213 is evaporated by passing the recording medium 213 through a nip between an upper drying roller 200 and a lower drying roller 201. A heat source for evaporating the moisture is a heater 210 using halogen. A temperature of the heater 210 is set to any set temperature by a temperature measuring element such as a thermistor (not shown) and a control circuit for switching the heater to turn ON/OFF in response to a temperature signal from the thermistor. When the recording medium 213 is conveyed to the nip of the pair of the drying rollers 200, 201, the recording medium 213 is heated and dried. In this case, since vapor is generated, surrounding air is discharged toward a direction shown by the arrow Q by means of a fan 207.
The dried recording medium 213 is guided by a convey guide 208 to be conveyed into a nip between an upper laminate roller 202 and a lower laminate roller 203. A laminate material 204 having a laminate layer is wound around a feeding roller 205. The upper laminate roller 202 includes a heater 211 therein and a temperature of the heater 211 is controlled to a predetermined value. When the recording medium 213 and the laminate material 204 are conveyed to the nip of the pair of laminate rollers 202, 203, the laminate layer of the laminate material 204 is adhered to a recorded surface of the recording medium 213. The laminate material 204 is cut by a cutter (not shown) when the laminate material passes through a pair of discharge rollers 206, thereby completing a recorded product having the recorded surface covered by the laminate layer.
However, the conventional image forming apparatus had the following problems. In the conventional image forming apparatus, the recording medium was dried by the pair of drying rollers before the lamination. In order to improve through-put of the image forming apparatus, it is required that the recording medium which absorbed liquid such as ink be dried quickly. In order to dry the recording medium adequately, it is general that the heating temperature of the drying roller pair is increased or a width of the nip between the drying roller pair and the recording medium is increased. However, if the heating temperature of the drying roller pair is increased, since temperatures of a back coat layer for increasing the quality after the output and of the material itself of the recording medium are also increased, there arose a problem that kinds of available recording media are limited. Further, there arose a problem that moisture is trapped between the back coat layer and the base material of the recording medium, with the result that a surface layer of the rear surface is partially swollen to deteriorate the quality greatly or to generate poor conveyance. Further, if the contact area between the drying roller pair and the recording medium is increased, there arose a problem that the apparatus itself becomes large-sized due to lengthened diameters of the drying rollers and a complicated arrangement for winding the recording medium around the roller is required. Further, if the heating temperature of the drying roller pair is increased, there arose a problem that power consumption of the apparatus is increased.
An object of the present invention is to provide an image forming apparatus in which a laminating speed can be increased without becoming the apparatus large-sized and useless energy consumption can be reduced while maintaining a required drying amount.
Another object of the present invention is to provide an image forming apparatus comprising laminate object conveying means for conveying an object to be laminated (referred to as xe2x80x9claminate objectxe2x80x9d), laminate means for effecting laminate processing on the laminate object, drying means for drying the laminate object before the laminate object is laminated by the laminate means, and means for changing a temperature of the drying means between before and when the laminate object is conveyed to the drying means.